WIP adding next_pc

Cargo.lock

@@ -210,6 +210,7 @@ name = "cpu"
 version = "0.1.0"
 dependencies = [
  "fayalite",
+ "serde",
 ]
 
 [[package]]
@@ -303,7 +304,7 @@ checksum = "e8c02a5121d4ea3eb16a80748c74f5549a5665e4c21333c6098f283870fbdea6"
 [[package]]
 name = "fayalite"
 version = "0.3.0"
-source = "git+https://git.libre-chip.org/libre-chip/fayalite.git?branch=master#edcc5927a5f9ebca6df5720bb1f5931e50095a57"
+source = "git+https://git.libre-chip.org/libre-chip/fayalite.git?branch=master#c11a1743f97b5219725d123d876effe717b633f2"
 dependencies = [
  "base64",
  "bitvec",
@@ -330,7 +331,7 @@ dependencies = [
 [[package]]
 name = "fayalite-proc-macros"
 version = "0.3.0"
-source = "git+https://git.libre-chip.org/libre-chip/fayalite.git?branch=master#edcc5927a5f9ebca6df5720bb1f5931e50095a57"
+source = "git+https://git.libre-chip.org/libre-chip/fayalite.git?branch=master#c11a1743f97b5219725d123d876effe717b633f2"
 dependencies = [
  "fayalite-proc-macros-impl",
 ]
@@ -338,7 +339,7 @@ dependencies = [
 [[package]]
 name = "fayalite-proc-macros-impl"
 version = "0.3.0"
-source = "git+https://git.libre-chip.org/libre-chip/fayalite.git?branch=master#edcc5927a5f9ebca6df5720bb1f5931e50095a57"
+source = "git+https://git.libre-chip.org/libre-chip/fayalite.git?branch=master#c11a1743f97b5219725d123d876effe717b633f2"
 dependencies = [
  "base16ct",
  "num-bigint",
@@ -353,7 +354,7 @@ dependencies = [
 [[package]]
 name = "fayalite-visit-gen"
 version = "0.3.0"
-source = "git+https://git.libre-chip.org/libre-chip/fayalite.git?branch=master#edcc5927a5f9ebca6df5720bb1f5931e50095a57"
+source = "git+https://git.libre-chip.org/libre-chip/fayalite.git?branch=master#c11a1743f97b5219725d123d876effe717b633f2"
 dependencies = [
  "indexmap",
  "prettyplease",

Cargo.toml

@@ -15,6 +15,7 @@ rust-version = "1.89.0"
 
 [workspace.dependencies]
 fayalite = { git = "https://git.libre-chip.org/libre-chip/fayalite.git", version = "0.3.0", branch = "master" }
+serde = { version = "1.0.202", features = ["derive"] }
 
 [profile.dev]
 opt-level = 1

crates/cpu/Cargo.toml

@@ -16,3 +16,4 @@ version.workspace = true
 
 [dependencies]
 fayalite.workspace = true
+serde.workspace = true

crates/cpu/src/config.rs

@@ -8,9 +8,10 @@ use crate::{
     },
 };
 use fayalite::prelude::*;
+use serde::{Deserialize, Serialize};
 use std::num::NonZeroUsize;
 
-#[derive(Clone, Eq, PartialEq, Hash, Debug)]
+#[derive(Clone, Eq, PartialEq, Hash, Debug, Serialize, Deserialize)]
 #[non_exhaustive]
 pub struct UnitConfig {
     pub kind: UnitKind,
@@ -27,12 +28,14 @@ impl UnitConfig {
     }
 }
 
-#[derive(Clone, Eq, PartialEq, Hash, Debug)]
+#[derive(Clone, Eq, PartialEq, Hash, Debug, Serialize, Deserialize)]
 #[non_exhaustive]
 pub struct CpuConfig {
     pub units: Vec<UnitConfig>,
     pub out_reg_num_width: usize,
     pub fetch_width: NonZeroUsize,
+    pub max_branches_per_fetch: NonZeroUsize,
+    pub fetch_width_in_bytes: NonZeroUsize,
     /// default value for [`UnitConfig::max_in_flight`]
     pub default_unit_max_in_flight: NonZeroUsize,
     pub rob_size: NonZeroUsize,
@@ -46,6 +49,18 @@ impl CpuConfig {
         };
         v
     };
+    pub const DEFAULT_MAX_BRANCHES_PER_FETCH: NonZeroUsize = {
+        let Some(v) = NonZeroUsize::new(1) else {
+            unreachable!();
+        };
+        v
+    };
+    pub const DEFAULT_FETCH_WIDTH_IN_BYTES: NonZeroUsize = {
+        let Some(v) = NonZeroUsize::new(4) else {
+            unreachable!();
+        };
+        v
+    };
     pub const DEFAULT_UNIT_MAX_IN_FLIGHT: NonZeroUsize = {
         let Some(v) = NonZeroUsize::new(8) else {
             unreachable!();
@@ -57,6 +72,8 @@ impl CpuConfig {
             units,
             out_reg_num_width: Self::DEFAULT_OUT_REG_NUM_WIDTH,
             fetch_width: Self::DEFAULT_FETCH_WIDTH,
+            max_branches_per_fetch: Self::DEFAULT_MAX_BRANCHES_PER_FETCH,
+            fetch_width_in_bytes: Self::DEFAULT_FETCH_WIDTH_IN_BYTES,
             default_unit_max_in_flight: Self::DEFAULT_UNIT_MAX_IN_FLIGHT,
             rob_size,
         }
@@ -117,3 +134,12 @@ impl CpuConfig {
             [self.non_const_unit_nums().len()]
     }
 }
+
+#[hdl(get(|c| c.fetch_width.get()))]
+pub type CpuConfigFetchWidth<C: PhantomConstGet<CpuConfig>> = DynSize;
+
+#[hdl(get(|c| c.max_branches_per_fetch.get()))]
+pub type CpuConfigMaxBranchesPerFetch<C: PhantomConstGet<CpuConfig>> = DynSize;
+
+#[hdl(get(|c| c.fetch_width_in_bytes.get()))]
+pub type CpuConfigFetchWidthInBytes<C: PhantomConstGet<CpuConfig>> = DynSize;

crates/cpu/src/lib.rs

@@ -2,6 +2,7 @@
 // See Notices.txt for copyright information
 pub mod config;
 pub mod instruction;
+pub mod next_pc;
 pub mod reg_alloc;
 pub mod register;
 pub mod unit;

crates/cpu/src/next_pc.rs

@@ -0,0 +1,117 @@
+// SPDX-License-Identifier: LGPL-3.0-or-later
+// See Notices.txt for copyright information
+
+//! [Next-Instruction Logic](https://git.libre-chip.org/libre-chip/grant-tracking/issues/10)
+//!
+//! The basic idea here is that there's a `next_pc` stage that sends predicted fetch PCs to the `fetch` stage,
+//! the `fetch` stage's outputs eventually end up in the `decode` stage,
+//! after the `decode` stage there's a `post_decode` stage (that may run in the same clock cycle as `decode`)
+//! that checks that the fetched instructions' kinds match the predicted instruction kinds and that feeds
+//! information back to the `fetch` stage to cancel fetches that need to be predicted differently.
+
+use crate::{config::CpuConfig, util::array_vec::ArrayVec};
+use fayalite::prelude::*;
+use fayalite::util::ready_valid::ReadyValid;
+
+#[hdl]
+pub enum PredictedCond {
+    Taken,
+    Fallthrough,
+}
+
+#[hdl]
+pub struct PredictedFallthrough {}
+
+#[hdl]
+pub enum BranchPredictionKind<CondKind> {
+    Branch(HdlOption<CondKind>),
+    IndirectBranch(HdlOption<CondKind>),
+    Call(HdlOption<CondKind>),
+    IndirectCall(HdlOption<CondKind>),
+    Ret(HdlOption<CondKind>),
+}
+
+#[hdl(get(|c| c.max_branches_per_fetch.get() - 1))]
+pub type NextPcPredictionMaxBranchesBeforeLast<C: PhantomConstGet<CpuConfig>> = DynSize;
+
+#[hdl(no_static)]
+pub struct NextPcPrediction<C: PhantomConstGet<CpuConfig>> {
+    pub fetch_pc: UInt<64>,
+    pub async_interrupt: Bool,
+    pub branches_before_last: ArrayVec<
+        BranchPredictionKind<PredictedFallthrough>,
+        NextPcPredictionMaxBranchesBeforeLast<C>,
+    >,
+    pub last_branch: HdlOption<BranchPredictionKind<PredictedCond>>,
+    pub last_branch_target_pc: UInt<64>,
+}
+
+#[hdl]
+pub struct NextPcToFetchInterfaceInner {
+    pub next_fetch_pc: UInt<64>,
+    pub in_progress_fetches_to_cancel: UInt<8>,
+}
+
+#[hdl(no_static)]
+pub struct NextPcToFetchInterface<C: PhantomConstGet<CpuConfig>> {
+    pub inner: ReadyValid<NextPcToFetchInterfaceInner>,
+    pub config: C,
+}
+
+#[hdl(no_static)]
+/// handles updating speculative branch predictor state (e.g. branch histories) when instructions retire,
+/// as well as updating state when a branch instruction is mis-speculated.
+pub struct NextPcToRetireInterface<C: PhantomConstGet<CpuConfig>> {
+    // TODO: add needed fields
+    pub config: C,
+}
+
+#[hdl(no_static)]
+pub struct NextPcToPostDecodeInterface<C: PhantomConstGet<CpuConfig>> {
+    // TODO: add needed fields
+    pub config: C,
+}
+
+#[hdl(no_static)]
+pub struct FetchToPostDecodeInterface<C: PhantomConstGet<CpuConfig>> {
+    // TODO: add needed fields
+    pub config: C,
+}
+
+#[hdl(no_static)]
+pub struct PostDecodeOutputInterface<C: PhantomConstGet<CpuConfig>> {
+    // TODO: add needed fields
+    pub config: C,
+}
+
+#[hdl_module]
+pub fn next_pc(config: PhantomConst<CpuConfig>) {
+    #[hdl]
+    let cd: ClockDomain = m.input();
+    #[hdl]
+    let to_fetch_interface: NextPcToFetchInterface<PhantomConst<CpuConfig>> =
+        m.output(NextPcToFetchInterface[config]);
+    #[hdl]
+    let to_post_decode_interface: NextPcToPostDecodeInterface<PhantomConst<CpuConfig>> =
+        m.output(NextPcToPostDecodeInterface[config]);
+    #[hdl]
+    let to_retire_interface: NextPcToRetireInterface<PhantomConst<CpuConfig>> =
+        m.output(NextPcToRetireInterface[config]);
+    todo!()
+}
+
+#[hdl_module]
+pub fn post_decode(config: PhantomConst<CpuConfig>) {
+    #[hdl]
+    let cd: ClockDomain = m.input();
+    #[hdl]
+    let from_next_pc_interface: NextPcToPostDecodeInterface<PhantomConst<CpuConfig>> =
+        m.input(NextPcToPostDecodeInterface[config]);
+    #[hdl]
+    let from_fetch_interface: FetchToPostDecodeInterface<PhantomConst<CpuConfig>> =
+        m.output(FetchToPostDecodeInterface[config]);
+    #[hdl]
+    let output: PostDecodeOutputInterface<PhantomConst<CpuConfig>> =
+        m.output(PostDecodeOutputInterface[config]);
+    todo!()
+}

crates/cpu/src/unit.rs

@@ -15,6 +15,7 @@ use fayalite::{
     intern::{Intern, Interned},
     prelude::*,
 };
+use serde::{Deserialize, Serialize};
 
 pub mod alu_branch;
 pub mod unit_base;
@@ -36,7 +37,7 @@ macro_rules! all_units {
         }
     ) => {
         $(#[$enum_meta])*
-        #[derive(Copy, Clone, Eq, PartialEq, Ord, PartialOrd, Hash, Debug)]
+        #[derive(Copy, Clone, Eq, PartialEq, Ord, PartialOrd, Hash, Debug, Serialize, Deserialize)]
         $vis enum $UnitKind {
             $(
                 $(#[$variant_meta])*